Rattling in the Rear End
 

So this has been happening since I got my car, I thought it was my exhaust rattling since it was kinda loose. I just replaced my exhaust and tightened everything up but it sounds like its getting worse. It sounds like a tin can rattling in my left rear wheelwell. It dosen't happen at very low speeds, but when I start going over 10 mph it gets very loud. I have no idea what would be the case, maybe a bearing or something?

Any advice would be great